Steam cleaning in a dishwasher

ABSTRACT

A preliminary steaming step is employed before a conventional dishwashing operation. The preliminary steaming step is conducted for 15-20 minutes, at a temperature of 100-150° C. and a pressure of 15 psi.

BACKGROUND OF INVENTION

[0001] 1. Field of Invention

[0002] The present invention relates to washing tableware, pots and pansin a conventional dishwasher and, more particularly, to employing anovel prolonged steaming step at the beginning of the dishwashingprocess to remove baked-on food.

[0003] 2. Art Related to Invention

[0004] Dishware, glassware, silverware, pots, pans and the like arenormally washed in a dishwasher using a series of steps that include hotwater, soap and heat to dry. The use of a steam cleaning or soaking stephas been suggested in U.S. Pat. Nos. 2,289,890; 4,457,323; 4,279,384;4,366,005; and 5,032,186. Generally, none of these references teachemploying a prolonged steaming step at the beginning of the conventionaldishwashing process.

SUMMARY OF INVENTION

[0005] It has now been discovered that by employing a preliminary,prolonged steaming step in a dishwasher prior to the conventionaldishwashing process that baked-on food is readily removed by aconventional dishwasher through the conventional washing process.

[0006] Broadly, the process of the present invention is a method foroperating a conventional dishwasher comprising the steps of:

[0007] (a) loading the dishwasher with items for washing;

[0008] (b) closing the loaded dishwasher;

[0009] (c) steam cleaning the items in a water saturated atmosphere at apressure of equal to or greater than 15 psi, a temperature of equal toor greater than 100° C., a time of equal to or greater than 15 minutes;and

[0010] (d) subsequently washing the steamed items in the dishwasher withsoap and water to clean said items.

[0011] As noted above, the steaming step of the present invention isdone in a conventional dishwasher prior to the conventionalwashing/rinsing, etc. cycles. In other words, the process of the presentinvention is done as a first step.

[0012] These and other aspects of the present invention may be morefully understood by reference to the following drawings and the detaileddescription and any examples that follows.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 illustrates a conventional dishwasher in which the processof the present invention can be conducted.

[0014] Referring to FIG. 1, the dishwasher of the invention isdesignated generally by the numeral 10 and is shown for purposes ofillustration as including tub 12 provided with downwardly-opening frontdoor 14. Dishes to be washed, rinsed and dried within tub 12 are adaptedto be supported therein by racks 16 and 18 accessible upon opening thefront door 14. Motor-pump assembly 20 is employed to remove water fromtub 20 during the conventional washing/rinsing steps and to deliverwater to distributing impeller 22 which sprays the water over dishes inracks 16 and 18. If desired, a second impeller, not shown, in serieswith impeller 22 may be located between racks 16 and 18.

[0015] Electrical resistance heater 24 is located within tub 12 adjacentthe bottom thereof and in communication with the interior of the tub,being suitably mounted on the bottom wall of the tub.

[0016] The structure of dishwasher 10 has been illustrated and describedin a superficial way only merely to outline the environmental setting ofthe invention. It will be understood that dishwasher 10 includesnumerous additional components, preferably electrically operated, forperforming such functions as introducing water into tub 12 at varioustimes during the operating cycle of the dishwasher, for draining thewater from the tub after each washing or rinsing operation, forcirculating heated air over dishes in racks 16 and 18 during the dryingoperation, and the like. These various operations are carried out underthe control of timer 26 located at the top of door 14 in the particularconstruction illustrated, and thermostat 28 located in the door andexposed to the temperature within the tub. The various electricallyoperated components of dishwasher 10, and their control elements, may beconnected in a conventional manner which is well-known in the householddishwasher art, a simplified illustrative example being shown in theaforementioned.

[0017] In order to generate the steam prior to the conventionalwashing/rinsing/drying step of the dishwasher, any conventional methodfor generating steam can be employed. For example, a body of water witha surface heater, a body of water with an immersion heater or a steamnozzle injection apparatus. Using heating elements such as the oneillustrated in FIG. 1 is taught in U.S. Pat. Nos. 4,457,323 or4,279,384, both of which are incorporated herein by reference, both ofwhich employ a heater such as heater 24 to heat a body of water andgenerate steam in the tub of the dishwasher. The '323 patent generatessteam by positioning the heater on top of the body of water and heatingonly the top of the water to generate steam while the '384 patent usesan immersion heater to generate steam.

[0018] As a specific example herein, FIG. 1 illustrates a surface styleheater such as the one disclosed in the '323 patent. Sump 30 holds waterto a level of 32.

[0019] When the bottom of tub 12 contains a static body of water in sump30 to level 32, heater 24 is only partially submerged and applies heatonly to a surface layer of a body of water, there being no substantialapplication of heat to the water below such surface layer.

[0020] Alternatively, heater 24 can be positioned in sump 30 such thatheater 24 is an immersion heater and is positioned below water level 32.Such is the teachings in the '384 patent.

[0021] As a further alternative, steam generating unit 40 injects steaminto tube 12 by way of nozzle 42. Steam generator unit 40 is aconventional piece of equipment that is operated in a conventionalmanner to inject steam into tub 12.

[0022] No matter which specific steam generating mechanism is employed,timer 26 controls the length that the steaming step is conducted. Thesteaming is conducted for a period of time equal to or greater than 15minutes and, more preferably, for a period of time between 15 and 30minutes. Good results have been obtained when steaming is conducted fora period of time between 15 and 20 minutes.

[0023] The temperature of the atmosphere in the tub must be such thatthe steam is maintained and the atmosphere is saturated with water.During the steaming step, the temperature of the atmosphere is equal toor greater than 100° C. (212° F.) and, more preferably, between 100° C.(212° F.) and 175° C. (350° F.). Good results have been obtained whenthe temperature is between 120° C. (250° F.) and 150° C. (300° F.)

[0024] The pressure of the atmosphere is greater than or equal to 15 psi(103,500 Pa).

[0025] The steaming step of the present invention is done first, beforethe conventional dishwashing cycles are run. In this way, the hard toremove, baked-on food is loosened such that the normal dishwashingcycles will remove the dirt and/or food matter from the items i thedishwasher.

[0026] The water employed for the steaming step should be clean, withoutfood/grease particles therein. Using clean water improves the efficiencyof heater 24 or steam generating unit 40.

[0027] Preferably, after the steaming step, the items are sprayed withhot water under the control of timer 26. Next, the items are subject toa conventional dishwashing operation. For example, they are subjected toa spray washing operation with detergent. Then, the items are rinsedwith hot water, rinsed with a rinsing agent, and dried. Heater 24 can beused to generate the heat used for drying.

[0028] It will be understood that the claims are intended to cover allchanges and modifications of the preferred embodiments of the inventionherein chosen for the purpose of illustration which do not constitute adeparture from the spirit and scope of the invention.

What is claimed is:
 1. A method for operating a dishwasher comprising:(a) loading a dishwasher with items in need of washing; (b) closing saidloaded dishwasher; (c) steam cleaning said items in a water saturatedatmosphere at a pressure of equal to or greater than about 15 psi, atemperature of equal to or greater than about 100° C., a time of equalto or greater than about 15 minutes; and (d) after said steaming,washing said items in said dishwasher with soap and water to clean saiditems.
 2. In a method for operating a dishwasher where items in a closeddishwasher are washed with soap and water and subsequently dried, theimprovement comprising steaming items in a closed dishwasher prior tosaid items being washed with soap and water, said steam cleaning beingconducted in a water saturated atmosphere, at a pressure of equal to orgreater than about 15 psi, a temperature of equal to or greater thanabout 100° C., and a time of equal to or greater than 15 minutes.